Nitroquinolines as dienophiles in polar Diels-Alder reactions. Influences of molecular solvents and ionic liquids

5- and 8-nitroquinolines are studied as dienophiles in polar thermal Diels-Alder reactions whit normal electron demand using several and structural different dienes, and chloroform as solvent media. A very strong electron-acceptor group, such as nitro group, push the dienophilic character of these heterocyclic compounds and owing to this substituent is easily extruded under thermal conditions. When the cited dienophiles were reacted with isoprene, 1-trimethylsilyloxy-1,3-butadiene and de Danishesfky diene, under different reaction conditions they showedtheir dienophilic character taking part in a normal demand DA cycloaddition reactions. These cycloaddition reactions were analyzed in presence of ionic liquids (IL´s). In this sense was used ethyl ammonium nitrate (NEA) as protic IL´s and another composed by 1-butyl-3-methyl-imidazolium [bmim] as the cation and tetrafluoroborate as the anion [BMIM] [BF₄]. The presence of IL´s improved the yields and the reaction conditions are softer.